This article from InternetNews.com points out an attempt by an advertiser to get regular references to their product/site from regular high traffic bloggers. Unless it is a clearly disclosed situation, I would be offended to find a post I am reading turns out to be a paid ad. The company says that the blogger can post a disclaimer if they like. Absent that, it has the elements of whoring your site. If you want sex for money at least yo u can say so! I hope the recipients do. They claim they will disclose who they are paying to post on the site FAQ.
The other interesting thing is that the advertiser says you don’t even have to say nice things about them to participate. That perhaps shows the true motivation, links for search engine improvement. The engines will elevate their rankings soley on the existence of links, so they don’t in fact care much what you say. The point is, you are relevant enough to improve their scores. Or, perhaps the idea was just to create buzz? If that was the goal they succeeded because I had not heard of them until today.
Interesting, very interesting!